Saw

ABSTRACT

A saw for performing chop cuts has a base, a cutting unit, and a pivot joint pivotally mounting the cutting unit to the base to enable the cutting unit to pivot towards or away from the base to perform chop cuts. The pivot joint has a cup-shaped section having an open end, a cap rotatably mounted on the open end of the cup-shaped section to form a sealed enclosed space within the cup-shaped section and cap, and a spring located inside of the sealed enclosed space. The spring is connected between the cup-shaped section and the cap. The spring applies a rotational biasing force between the cup-shaped section and the cap to urge relative rotation movement between the two.

FIELD OF THE INVENTION

The present invention relates to a saw with a pivot joint.

BACKGROUND

U.S. Pat. No. 5,720,096 discloses a typical chop saw. A chop sawtypically includes a base. A motor unit is attached to one end of an armwhich is pivotally mounted at the other end to a rear edge of the basevia a pivot joint. The motor unit comprises an electric motor whichrotationally drives a circular saw blade mounted on a spindle whichprojects from the motor unit. The motor unit is biased to an upperposition by a spring within the pivot joint. The motor unit can bepivoted downwards towards the base by an operator grasping a handleattached to the motor unit and urging it downwards against the biasingforce of the spring. The motor is activated by the operator using aswitch mounted on the handle, the motor being typically powered by amains electricity supply.

The work piece to be cut is placed on the base against a fence locatedtowards the rear of the base. The work piece may be clamped against thefence using an adjustable clamp. Such clamps are typically attached tothe base. Guards, attached to the motor unit, may surround part or allof the blade. A guard actuation mechanism may be utilized in order toretract the guards when the motor unit is pivoted downwardly. When themotor is activated and a work piece is secured on the base, the motorunit is pivoted downwards towards the base by an operator to perform achop cut on the work piece.

Other types of saw incorporate a pivot joint to enable the saws have achopping function and perform chop cuts, for example, a sliding compoundmiter saw. Such saws also require a pivot joint to enable the saw toperform chop cuts. EP2689880 discloses an example of such a saw andwhich has a pivot joint to enable it to perform chop cuts.

One problem with using chop saws or saws with a chopping function isthat they generate a lot dust and debris during the cutting process. Inexisting designs of pivot joints used on such saws, the build-up of dustand debris in and around the pivot joint can interfere with theoperation of the pivot joint. It is therefore intended to provide animproved design of pivot joint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a miter saw;

FIG. 2 shows an exploded view of the pivot joint of the miter saw from afirst perspective;

FIG. 3 shows an exploded view of the pivot joint from a secondperspective;

FIG. 4 shows an exploded view of the spring and cup-shaped section; and

FIG. 5 shows a schematic diagram of a cross sectional view of the pivotjoint.

DESCRIPTION

Referring to FIG. 1, the miter saw comprises a base assembly comprisinga base 6 and a rotatable table 100. The base 6 preferably has twoplatforms 12 formed symmetrically on either side of the base 6. Therotatable table 100 is preferably rotatably mounted on the base 6between the two platforms 12. The top surface 102 of rotatable 100preferably lies flush with the top surfaces 104 of the two platforms 12.The combined surfaces 102, 104 of the rotatable table 100 and platforms12, respectively, may form a work surface.

An extension arm 106 is rigidly attached to the rotatable table 100which extends forward in well-known manner. The rotatable table 100 andextension arm 106 can pivot about a vertical axis through a range ofangular positions. The angular movement is preferably restricted by theextension arm 106 engaging with one or other of the sides 108 of theplatforms 12.

A locking lever 120 can be used to lock the rotatable table 100 andextension arm 106 in desired angular positions. A scale 122 is attachedto the base 6 to indicate the angular position of the extension arm 106.Carrying handles 10 are attached to the sides of the base 6.

A mount 27 is preferably pivotally mounted on the rear of the rotatabletable 100. Two guide rods (not shown) may be pivotally attached to themount 27. A cutting unit 50 may be mounted to the mount 27 and/orslideably mounted on the two guide rods. Cutting unit 50 preferablyincludes a motor housing 68 in which is mounted an electric motor (notshown), guide rod support housing 110 in which are slideably mounted thetwo guide rods, and a blade guard 112 which surrounds a cutting blade124 which is mounted on an output spindle (not shown) of the motor. Themount 27 can pivot about a horizontal axis on the rotatable table toenable the saw to perform bevel cuts. The rods can pivot on the mountabout a horizontal axis to move the two rods and the cutting unit 50vertically away from or towards the rotatable table 100 and extensionarm 106 to enable the saw to perform chop cuts.

A spring 204, which forms part of the pivot joint, preferably biases themount 27 and guide rods to their highest position. A handle 114 may beattached to the front of the cutting unit 50 by which a user moves thecutting unit 50 towards or away from the rotatable table 100 andextension arm 106. The mount 27 preferably locks in automatically itsuppermost pivotal position by a latch mechanism (not shown). A pivotallever 116 may be mounted on the handle 114 by which an operator canrelease the latch mechanism. A switch 118 is preferably mounted on thehandle 114, the depression of which activates the electric motor.

A fixed fence 16 is preferably rigidly attached on top of the twoplatforms 12 of the base 6 at the rear of the platforms 12. The fence 16preferably extends across the rotatable table 100 but does not interferewith its rotational movement.

The pivot joint will now be described in more detail with reference toFIGS. 2 to 5.

The mount 27, which is preferably manufactured from aluminum, comprisesa curved wall 210 sealed at one end by an end wall 212 to form acup-shaped section 206 enclosing a tubular passage 208 of uniformcircular cross-section. Two walls 216, 218 may be formed around the openend of the cup-shaped section 206 to form a groove 214. An aperture 220is preferably formed through the center of the end wall 212.

A base 222 is preferably attached to the end of the two guide rods 200to hold the two guide rods 200 in position. The base 222 preferablycomprises two metal clam shells 224, 226 which are clamped around theend of the guide rods 200 and secured to each other and the guide rodsusing bolts 228.

One of the clam shells 224 preferably comprises a circular wall 230which connects to a circular base 232 formed on the side of the clamshell 224. The size and dimensions of the circular wall 230 are suchthat it is capable of mating with the groove 214 of the cup-shapedsection 206 as best seen in FIG. 5. When the circular wall 230 is matedwith the groove 214 of the cup-shaped section 206, the end of thecup-shaped section 206 abuts against circular base 232.

An elongate tube 234 preferably extends from the clam shell 224 at thecenter of the circular wall 230 and in parallel to the circular wall230. When the circular wall 230 is mated with the groove 214 of thecup-shaped section 206, the tube 234 preferably extends into the tubularpassage 208 as best seen in FIG. 5.

The pivot joint also includes the spring 204 which has a central coiledsection 234 and two straight ends 236, 238. When the pivot jointassembled, the circular wall 230 is preferably mated with the groove 214of the cup-shaped section 206. The spring 204 is preferably locatedinside of the tubular passage 208 with the coiled section surroundingthe tube 234.

One of the straight ends 236 preferably locates within a recess 240formed in the end wall 212 of the cup-shaped section 206 to attach it tothe cup-shaped section 206. The other straight end 238 preferablylocates in a second recess 242 formed in the clam shell 224 inside ofthe circular base 232 to attach it to the clam shell 224.

A bolt 244 may be passed through the aperture 220 in the end wall 212and through the tube 234. The head 246 of the bolt 244 preferablylocates against the outside of the end wall 212. A nut 248 and a washer250 are preferably screwed on the free end the bolt 244 and abut againstthe end of the elongate tube as best seen in FIG. 5. The bolt 244preferably secures the cup-shaped section 206 to the circular wall 230with the circular wall 230 mated with the groove 214 of the cup-shapedsection 206. When the bolt 244 secures the cup-shaped section 206 to thecircular wall 230, the clam shell 224 in combination with the cup-shapedsection 206 preferably form a sealed enclosed space 208 in which thespring 204 is located. The longitudinal axis of the bolt 244 ispreferably co-axial with the axis 202 of rotation.

The base 222 can pivot on the mount 27 about axis 202 by the circularwall 230 rotating around the groove 214 while remaining mated to it. Asthe base 222 pivots on the mount 27, the cup-shaped section 206 and/orthe circular wall 230 rotates around the bolt 244. The base 222 ispivotally supported on the mount 27 by the engagement of circular wall230 and the groove 214. As the circular wall 230 rotates within thegroove 214, one straight end 236 of the spring 204 rotates relative tothe other end 238, storing a spring force in the coiled section 234. Thespring 204 applies a biasing force between the cup-shaped section 206and the clam shell 224. The spring 204 is arranged to urge the two guiderods 200 to urge them to point upwardly and move the cutting unit 50 toits highest position. The angular movement of the base 222 on the mount27 is limited by a projection 250 on the base 222 travelling between twoend stops 252, 254 as the base 222 pivots on the mount 27. The spring204 preferably remains under tension regardless of the relative angularpositions of the base 222 and the mount 27.

While the present invention has been described in relation to a slidingcompound miter saw, it will be appreciated that it is applicable to anysaw where a pivot joint is required to enable the saw to perform chopcuts.

1. A saw for performing chop cuts comprising: a base; a cutting unit; apivot joint pivotally mounting the cutting unit to the base to enablethe cutting unit to pivot towards or away from the base to perform chopcuts, the pivot joint comprising: a cup-shaped section having an openend; a cap rotatably mounted on the open end of the cup-shaped sectionto form a sealed enclosed space within the cup-shaped section and cap;and a spring located inside of the sealed enclosed space and connectedbetween the cup-shaped section and the cap, the spring applying arotational biasing force between the cup-shaped section and the cap tourge relative rotation movement between the two.
 2. The saw of claim 1wherein relative rotation between the cup-shaped is section and the capin one direction increases the biasing force applied by the spring. 3.The saw of claim 2 wherein the spring always remains under tensionregardless of the relative angular positions of the cup-shaped sectionand cap.
 4. The saw of claim 1 wherein the cup-shaped section comprisesa curved wall sealed at one end with an end wall to form a tubularpassage.
 5. The saw of claim 1 wherein a circular groove is formedaround the open end of the cup-shaped section, the groove mating withthe cap when the cap is mounted on the open end of the cup-shapedsection.
 6. The saw of claim 5 wherein the cap is rotatably mounted onthe cup-shaped section.
 7. The saw of claim 1 wherein the spring) is ahelical spring comprising a coiled central section having two ends, oneend being connected to the cup-shaped section and the other end beingconnected to the cap.
 8. The saw of claim 7 wherein the cap is retainedon the cup-shaped section.
 9. The saw of claim 8 wherein at least one ofthe cup-shaped section and the cap rotates around the bolt as the caprotates on the cup-shaped section.
 10. The saw of claim 7 wherein thecap comprises an elongate tube which projects into the sealed enclosedspace, the coiled central section of the spring encircling the tube andthe bolt passing through the tube.